Yes, this is 100% a scam or rather, fraud (and may be illegal where you live).

He explains the con right in the follow-up email.

The reason for this proposal is that I had been working with several US collaborators on regular US software engineering roles using their profiles due to the high rate. After securing the positions, the work is subcontracted to me.

Let's break this down.

He gets people who would have nice resumes (or profiles,.. like a young fella fresh outta college) to apply for tech jobs. He's looking specifically for US tech jobs because of the "high rate" in which he means the jobs pay a high hourly rate/wage.

Once the company hires you, you subcontract (aka pay him) to do the work. Of course he's probably going to say something like, well you keep 20% of the "high rate" for yourself.

The following is only speculation

Since he's asking you about interviews and team meetings, I have a feeling he's not getting a lot of success recruiting "collaborators" in the US and likely thinks getting someone already in the US to recruit other will be easier (no language barrier, no international issue, etc). Having an American front man for this scam is likely going to make recruitment easier.

It feels a little sketchy to me.

The big question I’d want to know is if this is something where they use your face/communication to hide outsourcing work without the consent or knowledge of a company.

If that’s the case you could be on the hook for legal issues, but I think you’d be able to figure it out.

It’s also a tracked email from some service, so just beware that it’s probably not an individual sending these (how often do you use a third party email pixel when you email someone? This implies a pipeline of many people you want to iterate on).

And then while it’s fakeable using LLMs, they haven’t mentioned why YOUR profile is appealing, so it just seems mass spam to me.

"found your profile", as in, supposedly personalized, but the email is "tracked with Mailsuite" with an opt out link, indicating mass sending. Already suspicious.

From the description I broadly had a suspicion which was confirmed by the reply. They want you to be the employee or contractor and act as the face and communicator, while in an undisclosed matter, hidden from the employer, it's not you doing the work but them. It's a scam.

It's an impersonation scam that recently became somewhat popular. I don't remember where I've seen or read about it. Either some article(s) or YouTube.

I got this email before but for a Japanese person. I ignore them because it is scam

Did you check the mail headers? That can sometimes tell a story.

I mean, if your address already is on Github, nothing is lost by answering.

I'm planning a larger open source project (yeah, for a while now) and have a list of potential collaborators i want to ask then. Or is that a bad idea, unprofessional or something?

Looks reasonably legit to me. You can always ask for more details if you're interested. What exactly do they want you to do? What software is it?

It does feel slightly odd that someone would be spamming GitHub users for something like this, but you never know... Can't hurt to ask for more details anyway.