There's nothing wrong with linking to someone's web site....even if they have something to gain from it.....as long as you are a legitimate member of a web site and do something there to congtribute to the community aside from just spamming commercial links!
Personally, as a very experienced webmaster myself, I don't think you should worry about it too much.
Conditions: Reactive Arthralgia/Reactive Constellation, Chronic Pelvic Pain Syndrome, Sacroiliitis, Costochondritis, widespread Tendonitis, severe back pain & spasms with numerous spinal problems, barely able to type anymore due to severe full-body runaway inflammation, and on and on. Typical daily pain levels exceed 8.5(!)
Medications: Methadone, Dilaudid, Oxycodone, Marinol, Cesamet, Lidocaine Patches, Flexeril, Zanaflex, Soma, Desipramine; many herbs & supplements.
Previous medications: Oxycontin, Opana, Fentanyl patches, Kadian, Avinza, MS Contin, Lortab, OxyIR, Baclofen, Testosterone (oral, patches, gel), Cymbalta, Lyrica, Neurontin, Amitryptyline, every NSAID known to man, Prednisone....and many, MANY more.