Your friends are correct. Oregon taxes non-residents only on Oregon-source income. Work income is "sourced" where the work is actually (physically) performed. So Oregon does not tax the portion of your work income that you earn from work you perform in a location outside Oregon.
On your non-resident OR tax return, you would allocate to OR only the portion of your income attributable to work you performed inside Oregon.
If you've already submitted your OR return, and if it's been accepted, you can correct it (if necessary) by filing an amended OR return.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
