The difference between most open source software and altcoins is that when open source software is forked, the fork retains everything that the original had. Take OpenOffice and LibreOffice for example. An OpenOffice user had nothing to lose by switching to LibreOffice. Therefore the community benefits and everyone wins. When a coin is forked, everything is retained EXCEPT the original blockchain. When this blockchain dies, so do the investments of an entire community who believed in the old coin's success. If I were a Bytecoin investor, it would be in my best interests to see Monero die. If I were a Monero investor, the opposite would be true. If either coin becomes dominant over the other, the community wouldn't win. Rather, one community would win at the expense of the other.
This only means that the barrier to getting community support for a fork is higher, and when the community does support the fork, that is a stronger vote of "no confidence" in the original developer.
Anyone can fork anything, but no one can force the community to support the fork. That is up to the community.