Hello,
thanks to the work of Julien BLACHE and pkg-voip-maintainers group from Debian, OpenSER v1.1.0 is available via official Debian APT repositories with the unstable distribution.
http://packages.debian.org/unstable/net/openser
People liking to use default repositories can remove the openser.org site from sources.list. Beware that the version included in Debian does not include the TLS support -- integration of GPL and OpenSSL license to satisfy Debian policies being in progress. If you want to use the TLS version, stay with openser.org's repository for a while.
Cheers, Daniel