Paizo seems to be quite deliberately leaving this issue mostly to GM discretion, but the ambiguity of the rules could favor a "yes" answer to both scenarios you propose.
The rules address inter-ship teleportation and explicitly disallow only teleportation between two moving ships in combat. From the Teleport spell description:
Interplanar and interplanetary travel is not possible, and neither is travel between two moving Starships during combat...
Because the rules specify that teleportation between two moving starships in combat is not allowed, it is possible to infer that other ship-to-ship teleportation is allowed, such as between two moving starships not in combat, or between one moving and one stationary (or two stationary) starships that are actually in combat. However, the official Starfinder FAQ does not yet shed further light on this, so for now it would be the GM's call.
For teleporting between starships and planets, the Teleport spell description goes on to say:
...you might be able to teleport to a planet’s surface from an orbiting Starship.
The "might" suggests that the designers are deliberately leaving this to the GM's discretion for now. The ability to teleport from the surface up to a ship could cause problems for a GM in terms of allowing PCs a little too much power, or it could be fine, depending on the game and the GM. The vagueness of the rules, for now at least, makes it a GM decision. As for whether the reverse is possible--surface to starship--this is not addressed at all and thus also falls to the GM to decide, though the possibility of ship-to-surface and ship-to-ship (even moving ships) would logically open the door to surface-to-ship.
From a physics standpoint, a ship in geosynchronous orbit is moving, but may not be moving relative to the surface of the planet if the orbit is absolutely perfect. If the GM allows teleportation between moving ships that maintain a constant distance and bearing from one another, then he should logically allow teleportation from the surface to a ship in perfect geosynchronous orbit, assuming all other parameters for the spell are met (e.g., within range).
Paizo has actually decreased the rules clarity on this matter.
The Paizo online FAQ for Starfinder actually eliminates a sidebar on teleporting between starships from page 326 of the 1st and 2nd printing core rulebook and replaces it with a whole other topic. The original sidebar (which can be found on this page) explicitly stated that teleportation between ships was only possible if both ships were stationary. That language is now officially removed from the rules. This deliberate creation of additional ambiguity is further evidence that the designers wish to leave the matter of teleportation involving ships (other than maneuvering ships in combat) to the GM's discretion.
As a final note, keep in mind: being off target when teleporting to a ship could prove fatal.
Teleportation is stated to deliver the caster "safely" to a location, even if they are off target, but the off target distance as a percentage of the distance of the intended teleportation might mean the character can only appear in the void of space. In this case, "safely" might be interpreted to mean only not inside a solid object.