This is a false positive. It happens every time a new update is released. It will go away after a few days / a week, but for now updating may give this false positive.
See this post for more information: https://tpt.io/.316959 The post it geared towards Windows Defender, but the same applies to other antiviruses as well.
As an answer to your question, you don't "login" to multiplayer, if you are logged in to tpt you will also be logged in to multiplayer. If you joined multiplayer while logged out and got a guest nick, you'll have to restart tpt for tptmp to notice.
It's been a while since the last snapshot, so I released one. I also wanted to test the possibility to sign the mac version to prevent MacOS from nagging you every time you start TPT (+ add native support for M1 macs). Sadly it didn't work out so that change isn't included.
Snapshot 233 Fix cryptic Lua error built-in elements could sometimes produce Added chemically strengthening GLAS (expose GLAS to molten SALT) Element scroll bars no longer show in menus that don't scroll Fix find mode not highlighting WARP particles
Small changelog, but that's just because development is being done in an experimental branch that isn't ready for snapshots yet.
Bumping this thread because I just released a new snapshot. Fairly minor changes but we do appreciate it when people use and report bugs with the snapshots. Some of the bugfixes in this snapshot fixed bugs only present in earlier snapshots, the bugs got reported so now are able to be fixed before release.
Snapshot 236: Deprecate tpt.element_func / tpt.graphics_func and replace with compatibility script Mark saves with GLAS/QRTZ/TUNG as 97.0-only Fix handling of malformed scale: and proxy: arguments Add sim.partExists and elem.exists Add real v parameter to sim.partCreate Fix PIPE graphics hack giving Lua graphics functions bad particle IDs Fix exception when passing nil to some functions in interface api