EDIT:i tested wdctools and it's free ,maybe the others are free too .
It certainly does look like they only require you to register now in order to unlock the C compiler.
If that's really the case, then would be cool of them.
I took a look at their PDF manual explaining the compiler and program architecture ... and it looks a bit scary (in theory). It seems that they're doing a lot of copying of stuff between stacks every time a function is called or returned from.
That's probably an easy way to get full ANSI C compliance, but it sounds a bit slow.
The lack of banking and optimizations for the HuC6280 CPU and PCE programs would obviously effect us, too.
I'll be interested to hear opinions if someone tries playing with it.