One typeface, several separate permissions
Type is licensed by context of use, and each context is priced independently. A desktop licence covers installing the font to create artwork, typically capped by seat count. A webfont licence covers serving it to browsers, usually metered by monthly pageviews. App and ebook embedding, and broadcast use, are separate again. Buying the desktop licence and then serving the same file from your own server is the single most common violation in the field, and it is a licensing failure rather than a technical one.
The practical consequence for a website is that the font must be delivered under a webfont licence — either self-hosted with pageview metering, or served from the foundry's own delivery network. Both are legitimate; the second removes the metering problem and adds a third-party dependency in your critical rendering path.
Open licences remove the whole question
Open-source families under the SIL Open Font License — the bulk of what Google Fonts serves — can be used, embedded and self-hosted commercially without seat counts or pageview caps. For most projects that is not a compromise but the correct answer, and it removes an entire category of compliance risk along with a recurring cost.
