If Gmail proved anything, it was that people would, for the most part, accept any terms of service. Or at least not care enough to read the fine-print closely.
gpl does not prevent the owner from changing the licence later. (Unless it is also making use of someone else’s gpl components.)
For example, Qt has a free version which is under the GPL; and a paid version which is not. So if you were making software with Qt, if you were using the free version, you’d be compelled to also release your product under GPL. But you could then later switch to a paid subscription and rerelease under some other licience if you wanted to.
gpl does not prevent the owner from changing the licence later. (Unless it is also making use of someone else’s gpl components.)
For example, Qt has a free version which is under the GPL; and a paid version which is not. So if you were making software with Qt, if you were using the free version, you’d be compelled to also release your product under GPL. But you could then later switch to a paid subscription and rerelease under some other licience if you wanted to.