It is true it isn't decidable which means it would have to operate on a calculation limit. With the calculation limit which I already implemented it is impossible to write an infinite loop.
** it can call native code, there is no protection when native code is called and it will count as a single op unless the native code provides a means to provide an alternative weight for the call. **
A decidable language is the ideal. The question is what language to go with until we have a decidable language? If you implement WREN, please only do so on a temporary basis so that when a better language comes along it can be swapped out. It might work for Steem, for now, but if Tau releases with MSO over graphs then you have a better language. The thing is, we don't know if Tau will be a success, but I do like the approach and decisions taken by Ohad so far.