SENNA by Collobert + Weston do SRL. It's free for non-commercial use. Hoifung Poon's unsupervised semantic parser can be used for SRL. It's available as open-s

SENNA by Collobert + Weston do SRL. It's free for non-commercial use. Hoifung Poon's unsupervised semantic parser can be used for SRL. It's available as open-source (I think?), but will require more work out of the box to get it working. Namely, you'll have to train it on your data, and convert semantic parses to SRL.