I need to buy a company license correct

Whoever is using Scala needs to have a license. If you already have a license you buy nothing. If your client will never use the font internally they buy nothing. If your client needs to use Scala on every single desktop in the company then they need to negotiate a corporate license with FontFont.

My assumption would be that the company needs to buy that cut / weight of the typeface to use the logo correct?

No. You already paid for the didot license and used it to create a static logo. If the client is not actually using the font to create more graphics, they don’t need a license. The rare exception if if this particular font was purchased from a foundry like House or TypeTrust that requires an additional license for use in identitie.

Only the one who uses the font needs a licence. YOU have designed the logo, so YOU should have the licences. If you sell the result (the logo) to your customer, he doesn’t have to have a licence (if you have converted the fonts into paths). Only if the customer wants to use the font as his corporate typeface for example he needs to licence this font. If he only gets his logo in vector artwork he doesn’t need to licence the fonts used. But have a look in the EULA of the fonts if the modification of the font is allowed. And of course it is ilegal to give away any font-files.

In general the advice is spot on, but be aware that some foundries have additional fees if the font is used as the basis of a logo... http://www.houseind.com/fonts/licensing/pricing (scroll down)

Wow - thank you all for your insightful + helpful comments!

Essentially, I have licenses for each of these typefaces. That being said, there will be people within the company working with Scala - since that will be the new corporate typeface.

I will check in with the appropriate fonthouses, but thank you all so much for the information!

One last question - I used Scala Sans Caps for a descriptor in this logo - and tweaked it very subtly.

I have this license, but this company wants to purchase it as well - not to be used in communications, but solely for the purpose of the descriptor.

Can I just purchase a single license for them - since it will not be used elsewhere, and since it is a tweaked outlined version at this point?

I don’t understand your last question (no native speaker here). Does it mean they want to licence the font (to be sure) because it is used in the logo? That’s nice and should be supported, but it is not necessarily necessary, so to speak, in the sight of the law IMO.

Can I just purchase a single license for them - since it will not be used elsewhere, and since it is a tweaked outlined version at this point?

Read the EULA first. Some EULAs are totally non-transferable, so in theory, a designer cannot even purchase fonts on behalf of a client.