In my humble opinion, the good question is : is eAthena/rAthena stable/up-to-date enough to ask players for money ;< ?
Once upon a time, eAthena dev team launched a "bug tracking session" (it was about the PR1, a bit old I know xD) and tried to fix as much bugs as they could. Maybe a "code cleaning session" could be better than a pay2play system, in a first time ... (I could help, I'm really used to C language, but not really to the code of eA/rA :/).
And to answer to the initial topic : Imo, Yare, eAthena, oAthena, jAthena... were all made to allow people to play for free.... It would be really sad if people were able to use (free) contributions (customs, etc) of the community to earn money. (Well it's already the case with cash shops, but players are free to play without any fee ^^).