If you're not serving the font from your server, you're only displaying it to people who already own the font. For anyone else, the browser will drill down the font stack till it finds a matching font on the computer.
WebFonts and Licensing
A webfont is a font that is used online. What makes it different is that the font is formatted so that browsers can see and render it accurately. This is often called a dynamic font, because the creator and user must have the font to see it properly.
These fonts are often embedded in the design project to ensure this works properly. Fonts can be embedded by the designer (but most licenses do not allow for this), while others include hosted embedding (this is how most webfont services work).
The wording of the license will specify if you can embed the font on your site or not.
However, (unsolicited advice) as far as designing and developing goes, I'd probably recommend either embedding the font, or not including it at all. It makes it too hard to have a consistent experience across all devices, and also means you have to QA everything for both fonts (at least, you probably should, since different fonts will change the layout)
Helvetica (the second font in your stack) is not a standard font either. I would definitely rethink having the first two fonts be non-standard and non-embedded for the above reasons. You can try embedding "Helvetica Neue," which I've found is an excellent alternative to Helvetica, (but you will have to buy the font)
Here are some other alternatives you might want to check out:
Is there a free 'Helvetica Neue' alternative?