I am being recruited by a vendor who sells equipment and software to my current employer. My recruitment would not put me in a position where I would be selling or working on projects for the company I work for now. Assuming I act ethically, adhere to my confidentiality agreement, protect all trade secret information obtained in my current position, and I am not under any explicit agreements to the contrary - is it ok for me to pursue this position?
It's not entirely clear what your specific concern is, but yes, assuming you "act ethically in keeping any confidential and trade secret information" confidential/secret, then there should be no issues with you pursuing the new position.
Note that this doesn't mean that your employer will be happy if/when they eventually find out about it, but in most cases you will have just as much a right to pursue a position with the vendor as you would with any other company.
It may be the case that your company and the vendor company have an agreement to not poach each other's staff, but if this is the case then it's the responsibility of the vendor to abide by the terms of the agreement. So even if such an agreement exists between your company and the vendor, it's not something that you personally need to worry about. And the fact that it sounds like the vendor approached you strongly implies that no such agreement exists. Either that, or their recruitment person is about to get themselves into some trouble.
Anyways, yes, it's okay for you to pursue the position. If you're concerned about the possibility of unintentionally letting any sensitive information slip as part of the interview process, then you might want to insist upon signing a mutual NDA with the recruiter. That way, even if you fail to act ethically (either intentionally or otherwise), any sensitive information you disclose cannot be used or reproduced by the vendor. If you want to ensure you're doing right by your current employer, a mutual NDA is an easy way to do so.
It sounds as if there are no legal concerns on your side and since the company knows who your current employer is, they would know in pursuing you if there were any legal concerns on their side (Recruiting firms for instance often have written agreements not to poach from their customers). So you are probably safe to pursue it. I will remind you that you are under no obligation to tell them where your new position is when you leave.
Sounds like legally and ethically you are covered. Be aware if you move that the danger zones are often the grey areas - answering questions from former collegues, networking to connect people in the vendor company with people in your former (the customer) company who normally wouldn't be connected, or inadverently using inside knowledge in subtle ways that aren't a direct disclosure.
One thing that may be worth researching is whether your current employer has been litigious with regard to any non-compete agreement you may have signed. There are cases where employees have been sued for intellectual property or non-compete issues that are fairly nebulous and dubious. It's not a situation that would be likely to win a court case, but rack up enough legal fees, and you'll be in bad shape whether you win or loose and you can't necessarily count on your new employer to back you up. It's worth nosing around to see if your current company has a reputation for pulling such tricks.
If there were actual issues regarding this, there would or could be a severe negative impact with the new employer, the vendor. I'm not talking legal agreements, though quite often those are included in their contracts. I'm talking about the desire not to anger or alienate a paying customer and lose their business over hiring away an employee.
So.... the vendor is pursuing you for a position. I can't believe that they would be oblivious to issues, if there were any, and, certainly, they wouldn't be so foolish as to recruit you for a position that would be impossible for you to function in, if there would be bad blood over the hiring.
If it's okay with the vendor, I think it's safe to assume it's okay for you to pursue, because all the potential negative ramifications, some of them quite substantial, would fall on them, primarily.