And it works (close to) the exact same way at Dreamwidth: don't have a DW invite code or don't think you'll be blogging there, but do want a Reading (like an LJ Friends) Page and to be able to comment non-anonymously on DW users' posts? Create a DW openID account with your LJ username.
(If at some point you decide to get a proper DW account, you will then have to go around and ask the DW users you asked to give you reading access for their f-locked posts with your openID account to (also or instead) give you reading access to your brandnew DW account. That is, if you don't want to keep having to log out of your full-on DW account and log back in with your openID DW account to see the flocked posts by DW user X and then back out and in to post your own stuff. Because you can't (I don't think) just transfer over reading access from an openID DW account to a full-fledged DW account.)
no subject
(If at some point you decide to get a proper DW account, you will then have to go around and ask the DW users you asked to give you reading access for their f-locked posts with your openID account to (also or instead) give you reading access to your brandnew DW account. That is, if you don't want to keep having to log out of your full-on DW account and log back in with your openID DW account to see the flocked posts by DW user X and then back out and in to post your own stuff. Because you can't (I don't think) just transfer over reading access from an openID DW account to a full-fledged DW account.)