LGTM vs PullApprove: What are the differences?
LGTM: A simple pull request approval system for GitHub. LGTM is a simple pull request approval system using GitHub protected branches and maintainers files. Pull requests are locked and cannot be merged until the minimum number of approvals are received. Project maintainers can indicate their approval by commenting on the pull request and including LGTM (looks good to me) in their approval text; PullApprove: Approve Pull Requests with a comment. Just start a comment with "Approved" (or a custom regular expression) to sign-off without ever leaving GitHub. PullApprove can be configured by a .pullapprove.yml YAML file in the root of your repo. With it, decide exactly what "approval" means to your team.
LGTM and PullApprove belong to "Tools for GitHub" category of the tech stack.
LGTM is an open source tool with 936 GitHub stars and 92 GitHub forks. Here's a link to LGTM's open source repository on GitHub.