There have been lots of entries throughout lj_nifty's lifetime that point to off-site services that ask for your password in order to perform their service. Getting through the moderation system for this community is absolutely not an official LiveJournal endorsement of those services. The moderator(s) do give a cursory glance to the services that are posted about, and won't approve things that blatantly appear to be scams, but that does not mean that anything that is approved for posting is to be automatically trusted.
Also, while this is an "official" community, it is run by a volunteer (me) for the purposes of pointing out nifty LJ-related stuff. No off-site tool/service posted here, unless otherwise stated by a LiveJournal employee, is officially endorsed or officially trusted.
Whether you share your password is up to you. LiveJournal's official stance is that you shouldn't share your password, because it creates an insecurity for your account, and I concur with that.
If you're concerned about your account's security, I recommend you read this FAQ: How do I choose a secure password? How do I keep my account secure?