MBA Recommendation Issue

I don't see why the adcom should not trust the second recommender so long as he gives a fair opinion about you ( without bragging/ unnecessarily overpraising). As MBAprepCoach already pointed out, get an official email address. Also, there is no conflict of interest. The recommnder should feel happy for you that your are working towards uplifting your career. You may also continue supporting the NGO while at bschool and that he something he should feel proud about.
2. That sounds ok. Just let it be known that he is senior to you and therefore somewhat a mentor.
3. I dont see a problem with mentioning that you are a cofounder. Perhaps you are getting overly concerned about this issue. On the contrary, i feel being a cofounder requires a different set of initiative, skills and resilience, as compared to being only a volunteer. You will miss out on that aspect by not mentioning that you are a cofounder. Moreover, some bschools such as Darden require you to have a leadership section on the resume where the word cofounder is going to look weighty, especially if you have made substantial impact through the NGO.
I'd end by saying, get the other cofounder to give meaty and real examples to support your strengths and weaknesses and you shall be ok.

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Hello AllRight,

Hope this finds you well.

The second recommendation would help add another perspective and would be value-adding from that viewpoint. Ensure that the recommendation goes out from a professional email id, touches only on professional elements, and states the facts as they stand.

It is absolutely alright to provide a recommendation from a co-founder so you need not worry about the Ad Com trusting you.

Good luck!

AllRight:

1. Will admissions committees really trust my second recommendation? (I mean the conflict of interest due to opinion from other cofounder)

A: Yes, trust is not really the core issue here.

2. Is it enough to explain that the co-founder is the chief executive and I am his deputy and another co-founder, so that there is no doubt?

A: Yes, just be clear about the relationship. If the relationship is really 1a and 1b, that's fine. Even if it were 1a and 1a that would also be fine. Not everyone has an opportunity to get a second superior to write a letter of recommendation. Sometimes founders have to ask customers. Don't worry about the relationship as much as the clarity of the role.

3. We are a non-profit organization and the title co-founder does not play such a role as in the business environment. So, I can simply avoid mention the fact that that I am a co-founder at all.

A: Why? I think you're looking way into this matter. What matters here is the core content of who you are, how you operate, and how you are successful. All this title, hierarchy, etc. is just context so the AdCom understands who is writing the letter what is their relationship to you.