If I join JAMMS can I still negotiate a license with a webcaster if I want to?

Yes. Although membership in JAMMS prohibits you from licensing your sound recording copyrights to another royalty collective for purposes of collecting and distributing, your membership in JAMMS does not in any way limit your ability to enter into direct licenses of any sound recordings that you own, whether with webcasters or other potential licensees. JAMMS simply requires that SRCOs notify it of any direct licenses entered into with statutory traditional licensees or digital music service providers so that it can ensure that payments received from services that hold direct licenses to certain recordings are calculated correctly and allocated properly.