[hokkos]

I hope they will open source Microsoft.Automata too, it was very useful for a project where I had to generate samples of strings that had to conform to multiple regex :

http://research.microsoft.com/en-us/projects/automata/

[porges]

There are potentially patents on the code, e.g. https://www.google.co.nz/patents/US8515891 which discusses PEX + regex (mentioning SMT solvers).