That reference was in reference to post # 24. For the world Maula/Wali you can refer to the 2nd reference I posted in post # 27.
Word Maula has many meanings but generally it is used to indicate authority. It is obvious that Allah (swt) is the Master of all things and He is the only and the ultimate authority. However when Muhammad (saww) said he is our mawla, and then Ali is our mawla too, this is not equating it with the fact that Allah (swt) is the Master of all things. This means they are the masters, as masters are to students, that they are the guides to Islam. If you want to study the grammar of the word then it is discussed in Al Mizan: http://www.shiasource.com/al-mizan/self/tafsir-5-55-56/. I will quote you a passage.
"QUR’AN: Only Allah is your Guardian and His Messenger and those who believe: ar-Raghib has said in his Mufradatu’l-Quran: “al-wilayah” and “at-tawallah” denote that two or more things are so positioned as nothing extraneous comes between them. Metaphorically it is used to indicate proximity in place, or affinity, or friendship, and in help, or in belief al-wilayah is help, and/or management of affairs. It has been said that al-walayah and al-wilayah both are one like al-dalalah and al-dilalah and it really means management of affairs; and al-waliyy add al-mawla denote this meaning, and both are used as nomen agentis, i.e. guardian/manager; and as nomen patientis, i.e. one whose affairs are managed. A believer is called waliyy of Allah, but nowhere is he referred to as mawla of Allah; while Allah is called waliyy of the believers, as well as their mawla.
Further he says: “They say, tawalli when used without any preposition, gives the meaning of wilayah, indicating that it is related to the nearest objective; they say, 'I turned my ears/eyes/face to so and so. Allah says: …so We shall surely turn thee to a qiblah which thou shall be pleased with; turn then thy face towards the Sacred Mosque; and wherever you are, turn your faces towards it,… (2:144); but when it is followed by preposition min (from) clearly or implied, it means turning away and leaving the proximity.”
Apparently, man perceived the proximity (pointed to by wilayah first of all physically in bodies and their places and times; then it was borrowed for immaterial nearness, opposite to the abovementioned idea. We know that primitive man began his perceptive journey with the material things perceived through the five senses and was involved with them long before thinking about rational propositions and immaterial ideas and their related things.
When wilayah - a special proximity - is affected in spiritual/ immaterial affairs, it follows that Analyst has a right and an authority over the mawla, which others do not have (except through him). All such managerial aspects that may be delegated to another will automatically be taken over by the waliyy e.g. the waliyy of a deceased person. The estate, which the deceased used to manage by right of ownership, his heir, has the right to manage it by wilayah of inheritance. Likewise, the guardian of a minor manages that minor’s financial affairs by wilayah of guardianship; and the helper manages the affairs of the helped one strengthening him in his defense; and Allah is the Guardian (waliyy) of His servants and manages their affairs in this world and the hereafter ? there is no guardian except Him. So Allah is the Guardian of the believers, inasmuch as He manages the affairs of their religion through guiding, calling, and helping them and so on. And the Prophet is the Guardian of the believers inasmuch as he has the authority to decide between them, for them and against them through legislation and judgment. Likewise, the hakim (ruler, judge) is the guardian of the people over whom he rules within his jurisdiction. The same is the case with other examples of wilayah, like that of emancipation, covenant, protection, neighborhood and divorce; similarly, the wilayah of a cousin, of love and of a designated successor, and so on.
Also, His word: they shall turn (their) backs to you (33:15), i.e. they shall turn their backs towards the war and ignore its demands.
And His word: you turned back (5:92), i.e. you turned away from accepting it; you faced its opposite direction by turning away from it.
In short, looking at wilayah in its different usages, we get the meaning of a sort of proximity that gives its subject some authority of management and possession of planning.
Looking at the context of the verse under discussion: “Only Allah is your Guardian and His Messenger and those who believe”, we find that the meaning of wilayah (guardianship) for all the guardians is the same, because “Allah, His Messenger and the believers”, have all been ascribed to one word: “your Guardian”, and clearly guardianship of each has the same meaning. This is also supported by the clause at the end of the second verse: then surely the party of Allah are they that shall be triumphant, as it indicates or clearly shows that all the guardians are the party of Allah, because they are under His Guardianship; thus the guardianship of the Messenger and of those who believe sprout from the root of Allah’s Guardianship."