as long as it works the same across all platforms, it shouldn't matter. Though I like the nice threat from Pocket Soft in their latest news item:
emailed Pocket Soft about this, and as well as the obvious "you're using an old version" response, and "open source software has no support" arguments, they also said something along the lines of: "xdelta likely infringes on our patents as well", implying that using it may be illegal.
It is only illegal if Pocket Soft provides verifiable evidence of infringed upon code.