Ruby-OCI8 is maintained by Kubo [email@example.com|http://forums.oracle.com/forums/#]. You can send email to him or to the Ruby-OCI8 developer mailing list
[firstname.lastname@example.org|http://forums.oracle.com/forums/#]. AFAIK, TAF is not supported yet. BTW, DRCP feature is supported in Ruby-OCI8.
I've been using Rails with Oracle 10g / XE and all my tests seem to show that TAF works out of the box.
I even got a problem where TAF (i think) wants to recover connections broken (due to innactivity timeout) by a firewall. This thing leads to another 8~10 minute timeout (which I think is related to the TCP implementation in Solaris 10)
To enable TAF you only have to configure it in your tnsnames.ora. I don't think you have to change anything in your code.