The reason for the "any lawful act" language is to allow the ASF to do things like run a conference, accept donations, sell t-shirts and other activities. If the statement was only "develop open-source software" there are all kinds of important activities that support open source development that would be impossible.

The fact is, however, that certificates can be changed by the people who can vote. IN the case of the ASF, the members are the ones who vote. Getting those ~800 members to radically trash the traditional goal of the foundation is not going to be possible as long as the current membership is active.