The lame MP3 encoder is freely distributable for non profit organisations or individuals. Cakewalk provide a utility and the complete set of instructions how you can personally install the free lame encoder. no cost involved. However if you want to have it installed without hassle then read on:

As soon as its bundled with or installed in a software package for sale it requires that vendor to pay a licence fee per unit sold. That would mean for a product like Sonar where many people have had continuous upgrades for 15 years you would be paying that fee as part of your Sonar upgrade every year or new version you bought. That's what all vendors who include it do.

Cakewalk's thinking is, this way you just buy a licence once but it's your licence not Cakewalk's. Do once and forever.
As far as I'm aware, if you had Cakewalk Pro Audio 9 then you were good for the included MP3 encoder upto but not including the Sonar X series. If you don't have Pro Audio 9 then you buy the MP3 unlock licence once these days only 9.95. The only time you would need contact Cakewalk is when you migrate from 32 bit to 64 bit as you need a different MP3 unlock licence.

I didn't really notice anyone slamming mp3s. The fact is it is a lossy compressed audio format. The only rate that is close to wav pcm 16bit 44.1khz is 320kbits and for distribution and Internet play engines that's usually too big a file still to use. Try 128 kbits.

Sound forge doesn't use Lame I think. As far as I'm aware they licence the Frauenhoffer encoder. It has awesome MP3 manipulation features. The batch file conversion and processing is just fabulous.

That's also a reason that it's included in the package because it's a commercial product and the encoder is not licenced under the GNU open source licence.